The collapse of a landslide dam can pose a significant threat to downstream areas,and it is necessary to thoroughly study the overtopping and collapse processes.The Baige landslide dam on the Jinsha River in 2018 is taken as a reference for experimental gradation.Improvements are made to address the limitations of the landslide lake's small shape factors and fine maximum particle sizes of in current laboratory tests.The independent variables selected are different upstream inflow rates,initial shapes of the spillway,and maximum reservoir water volume.A model test method is employed to analyze the collapse process,peak flow,and dam erosion rate.The results show that the upstream inflow rate is positively correlated with the timing of peak flow,with higher inflow leading to earlier peak flow.The triangular spillway,due to its greatest erosion intensity,results in the highest peak flow and earliest occurrence time within the group,while the trapezoidal spillway has the lowest peak flow and latest occurrence time,with the rectangular spillway falling in between.Coarse particles help delay the longitudinal failure of the dam under small shape factors,but this delaying effect rapidly diminishes as the shape factor increases.A larger shape factor of the landslide lake not only increases the dam erosion rate and causes significant sediment accumulation in downstream channels,but also leads to earlier peak flow occurrence and a sharp increase in peak flow.